Metal clad polymeric substrates for use in circuit laminates are known. Metallized polymeric laminates may be constructed by melt lamination techniques or by additive processes such as vacuum deposition or electroless deposition.
In each of the conventional methods adhesion between the substrates and metal layer is provided by mechanical interlocking of the metal layer and the surface substrate, i.e., adhesion is a function of substrate surface roughness. In some applications, e.g., high frequency circuits, a smooth metal/polymeric interface is desirable. None of the conventional methods provide a smooth metal/polymeric interface and acceptable adhesion.
Melt lamination techniques suffer from an additional drawback in regard to metallizing high temperature polymeric substrates. The coefficient of thermal expansion mismatch between the substrate and the metal layer results in stress formation within the laminate as the substrate is cooled from the melt to room temperature.
What is needed in the art, particularly in regard to high performance laminates for microwave applications, is a way to overcome the above deficiencies.